Investigation of the Potential of Heterophil/Lymphocyte Ratio as a Biomarker to Predict Colonization Resistance and Inflammatory Response to Salmonella enteritidis Infection in Chicken

Abstract

Salmonella causes significant economic loss to the poultry industry and represents a real threat to human health. The region of difference 21 (ROD21) pathogenicity island removal is a genetic mechanism by which Salmonellaenteritidis (SE) invades the intestinal epithelium and induces systemic infection in mice. The heterophil/lymphocyte (H/L) ratio reflects the chicken’s robustness and immune system status. The H/L ratio is considered a disease resistance trait, and it could be used as a marker for selecting Salmonella resistance in live chickens. However, the association of the H/L ratio with Salmonella resistance and the inflammatory response remains to be elucidated. Moreover, the kinetics of ROD21 excision in the intestine and immune organs of chickens is unknown. Therefore, this study aimed to investigate the bacterial load, the ROD21 excision, the IL-1β, IL-8, and INF-γ blood serum concentration kinetics, and the association with the H/L ratio in chicken at 1, 3, 7, and 21 days post-SE infection. The results showed a significant correlation between the H/L ratio and the bacterial load in the ileum and caecum at 7 dpi. The ROD21 pathogenicity island absolute and relative excision in the caecum were positively correlated at 1 dpi but negatively correlated at 7 dpi with the H/L ratio. However, in the liver, we found the opposite tendency. The association of the H/L ratio with IL-1β, IL-8, and INF-γ blood serum concentrations showed that a low H/L ratio is correlated with increased IL-1β and INF-γ at 21 dpi. This study confirmed that the H/L ratio is associated with robustness and Salmonella-resistance in chicken. The methodology used in this study can separate individuals into susceptible and resistant and can help in the selection and breeding of Salmonella-resistant chickens.

Heterophil/Lymphocyte Ratio Level Modulates Salmonella Resistance, Cecal Microbiota Composition and Functional Capacity in Infected Chicken

“…These observations suggest that low H/L ratio chickens are more resistant to Salmonella infection than high H/L ratio chickens. These results are in accordance with the previous studies ( 21 , 26 , 47 , 48 ). The H/L ratio is an immune feature that can reflect the resistance and immune response capacity.…”

“…Previous studies demonstrated that chickens and others avian species with low H/L ratio are more resistant to environmental stressors than birds with high H/L ratio ( 23 , 24 ). Recent researches even reported that a low H/L confers resistance advantages such as enhanced immune response, performances, adaptability, long life span and survival ( 25 , 48 ). In the present study, we hypothesized that the H/L ratio is associated with the microbiome composition, which provides the differential resistance observed between individuals with high and low H/L ratios.…”

Effect of rearing systems on immune status, stress parameters, intestinal morphology, and mortality in conventional and local chicken breeds

“…Heterophils and lymphocytes are the 2 most abundant white blood cell types in birds, which play an essential role in innate and adaptative immunity, respectively ( Minias, 2019 ). Stress increases heterophiles and reduces lymphocytes ( Mosca et al, 2019 ), and H/L is considered a disease resistance trait ( Thiam et al, 2022 ). Therefore, the increased H/L we observed in the free-range reared Ross is indicative of a state of stress and a reduced ability to cope with microbial diffusion and pressure ( Minias, 2019 ) in this housing system.…”

Effects of a Dietary Multi-Strain Probiotic and Vaccination with a Live Anticoccidial Vaccine on Growth Performance and Haematological, Biochemical and Redox Status Indicators of Broiler Chickens

“…Heterophils and lymphocytes are the most abundant WBC types in birds, and they play an essential role in innate and adaptative immunity, respectively. Heterophils are highly phagocytic and are involved in the acute inflammatory response as the first line of immune defence, mainly during the first hours following an immunological challenge [ 39 , 40 ]. In contrast, lymphocytes are involved in humoral adaptive immunity (B cells) and cell-mediated adaptive immunity (T cells).…”